This invention relates to a method for supplying an electrostatic precipitator with high voltage pulses generated by exciting the primary winding of a high voltage transformer having a secondary winding coupled to the electrostatic precipitator. The invention further relates to apparatus for supplying an electrostatic precipitator with high voltage pulses, in which apparatus a primary winding of a high voltage transformer with a secondary winding coupled to the electrostatic precipitator can be excited with energy transmitted from a d-c voltage source via a d-c control element or switch operated by a control unit.
It has been found that the degree of dust separation in electrostatic precipitators can be increased by subjecting the electrodes to high voltage pulses of variable amplitude and frequency as well as to a d-c voltage maintained as close as possible to the breakdown or arc-over limit of the electrodes.
The high voltage pulses generate additional charge carriers in the electrostatic precipitator without provoking the development of an arc. The high voltage pulses are usually produced by exciting the primary winding of a high voltage transformer which has a secondary winding coupled to the precipitator. Such an apparatus is disclosed for example, in German Patent Document (Offenlegungsschrift) No. 32 46 057, corresponding to commonly owned U.S. patent application Ser. No. 550,616 filed Nov. 10, 1983.
In practice, the problem is now encountered frequently that the core material of the high voltage transformer of such a supply apparatus is successively driven into magnetic saturation by the transmitted pulses, inasmuch as the pulses are generally unipolar, i.e., they have only a voltage increasing effect. With the prevailing high pulse frequencies, the saturation state is reached quickly with the result that further pulses no longer arrive at the electrostatic precipitator or arrive only with unsatisfactory quality, whereby the efficiency of the device is reduced.
An object of the present invention is to provide an improved apparatus and a corresponding improved method for supplying an electrostatic precipitator with high voltage pulses.
Another object of the present invention is to provide such an apparatus and such a method which ensure a constant high quality of high voltage pulses transmitted to the electrostatic precipitator.
Yet another, more particular object of the present invention is to provide such an apparatus and such a method in which magnetic saturation effects are reduced in a transformer coupled between a d-c voltage source and the electrostatic precipitator.